Flat acoustic transducer and method for driving the same

A flat acoustic transducer (100) includes a permanent magnet (10) and a magnetic member (20), which are arranged adjacent to each other with a predetermined interval, a flat vibrating membrane (30), provided facing the permanent magnet (10) and the magnetic member (20), and at least one coil (40), fixed to the vibrating membrane (30). In the flat acoustic transducer (100), an electrical signal is applied to the coil (40), to obtain vibration force (F) on the vibrating membrane (30) by way of a magnetic flux Φ generated between a magnetic pole face (12) of the permanent magnet (10) and the magnetic member (20), a step (50) is provided between the magnetic pole face (12) and the upper face (22) of the magnetic member (20), while at least part of a winding (42) of the coil (40) at the time of no application of an electrical signal is arranged inside the step (50).